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Shiba, Tomooki; Kaburagi, Masaaki; Nomi, Takayoshi; Suzuki, Risa; Kosuge, Yoshihiro*; Nauchi, Yasushi*; Takada, Akira*; Nagatani, Taketeru; Okumura, Keisuke
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 3 Pages, 2022/10
Nauchi, Yasushi*; Nomi, Takayoshi; Suzuki, Risa; Kosuge, Yoshihiro*; Shiba, Tomooki; Takada, Akira*; Kaburagi, Masaaki; Okumura, Keisuke
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 4 Pages, 2022/10
Pshenichnikov, A.; Kurata, Masaki; Nagae, Yuji
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 4 Pages, 2022/10
The CLADS-MADE-04 is the next test in the series aiming at understanding of the melt propagation behaviour in the lower core region. In this contribution, recent results of the post-test analysis including microstructure of metallic debris investigated by Electron Probe Micro Analyzer (EPMA) are discussed. During the test, melting of the control blade happened with sudden wave of strong heat release relatively slowly (several cm/min) spread from the hottest area downwards along the degrading control blade and channel box consuming the walls made of Zircaloy-4. A significant damage happened with the sample supporting plate as well. The investigation of microstructure of such metallic debris would allow understanding of a mechanism of enhanced local core degradation. The nature of strong heat release and possibility of spreading to the surrounding materials is to be confirmed after thorough phase identification by EPMA. The difference between Fe-B eutectic debris and Zr-Fe eutectic debris will be outlined. It is especially important for understanding of the lower core plate melt-through and a possibility of a Zr-Fe molten material progression into the lower plenum.
Suzuki, Kenta; Yashiro, Hiroshi*; Kawabata, Kuniaki
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 4 Pages, 2022/10
Porcheron, E.*; Leblois, Y.*; Journeau, C.*; Delacroix, J.*; Molina, D.*; Suteau, C.*; Berlemont, R.*; Bouland, A.*; Lallot, Y.*; Roulet, D.*; et al.
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 5 Pages, 2022/10
One of the important challenges for the decommissioning of the damaged reactors of the Fukushima Daiichi Nuclear Power Station (1F) is the fuel debris retrieval. The URASOL project, which is undertaken by a French consortium consisting of ONET Technologies, CEA, and IRSN for JAEA/CLADS, is dedicated to acquiring basic scientific data on the generation and characteristics of radioactive aerosols from the thermal or mechanical processing of fuel debris simulant. Heating process undertaken in the VITAE facility simulates some representative conditions of thermal cutting by LASER. For mechanical cutting, the core boring technique is implemented in the FUJISAN facility. Fuel debris simulants have been developed for inactive and active trials. The aerosols are characterized in terms of mass concentration, real time number concentration, mass size distribution, morphology, and chemical properties. The chemical characterization aims at identifying potential radioactive particles released and the associated size distribution, both of which are important information for assessing possible safety and radioprotection measures during the fuel debris retrieval operations at 1F.
Journeau, C.*; Molina, D.*; Brackx, E.*; Berlemont, R.*; Tsubota, Yoichi
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 5 Pages, 2022/10
CEA has manufactured a series of Fukushima Daiichi fuel debris simulants, either with depleted uranium oxide or with hafnium oxide as a surrogate of UO
. In ex-vessel compositions resulting from an interaction between corium and concrete, the oxidic phase density becomes lighter than that of the metallic phase, which segregates at the bottom. Three of these metallic phases have been mechanically cut at CEA Cadarache with handsaw and with core boring tool in FUJISAN facility. It appeared that two of these metallic blocks were extremely hard to cut (one from a fabrication with uranium oxide, the other from a simulant block) while the last one was more easily cut. The similarities and differences in metallographic analyses (SEM-EDS and XRD) of these three metal blocks will be presented and discussed. This experience provides useful learnings in view of the cutting and retrieval of fuel debris from Fukushima Daiichi.
Bando, Yamato*; Sasaki, Ryotaro*; Fukuda, Takanari*; Yamaji, Akifumi*; Yamashita, Takuya
no journal, ,
Yanagisawa, Kayo; Matsueda, Makoto; Furukawa, Makoto*; Hirata, Takafumi*; Takagai, Yoshitaka*
no journal, ,
LA-ICP-MS technique, both the elemental and isotopic mapping analyses can be made with high sensitivity over the traditional techniques such as XRF, EPMA, and SIMS. However, detection of Sr-90 is still challenging because of contributions of spectral interferences and tailing from neighboring abundant isotopes. To reduce the contribution of various interferences, ICP-MS/MS and reaction cell technique was adopted in this study. With the present analytical technique, the detection limit obtained from analysis area (100
100 
m square) was 0.64 mBq. The measured background intensity at m/z 90 u (1.6
2.2 cps) did not change significantly even under the presence of various interfering elements (Ni: 
2,084 mg/kg, Ge: 21 mg/kg, Y: 23,004 mg/kg, Zr: 175 mg/kg). The measured abundance sensitivity on Sr-90 from Sr-88 was 2.6e-9. The data indicates sensitive and rapid analytical technique for the mapping analysis of both Sr-90 and other trace-elements.
Sato, Takumi; Yamashita, Takuya; Shimomura, Kenta; Nagae, Yuji
no journal, ,
Yamada, Taichi; Abe, Hiroyuki*; Kawabata, Kuniaki
no journal, ,
Takahatake, Yoko; Koma, Yoshikazu
no journal, ,
The radioactive nuclides dispersed without control to on- and off-site of Fukushima Daiichi Nuclear Power Station (F1NPS) at its accident in 2011. A large amount of radioactive solid waste has been generated during its decommissioning. Radioactivity inventory of the solid waste should be estimated for R&Ds on waste management. Cobalt-60 is often selected as a key-nuclide for determining activity in solid waste generated at nuclear power plant, and is also detected in various F1NPS waste. In this study, radiochemical analysis data opened to public was investigated for correlation between Co-60 and nuclides of activation and fission products as well as actinides (H-3, C-14, Ni-63, Sr-90, Tc-99, I-129, Cs-137, Eu-154, Am-241, Pu-239+240). Cobalt-60 well correlated with Ni-63, Eu-154, Am-241 and Pu-239+240 in spite of differences in physical/chemical properties and process of contamination. This finding suggests a possibility to apply Co-60 as a key-nuclide of scaling factor method.
Sato, Yuki
no journal, ,
particle diameters by an alpha particle imaging detectorMorishita, Yuki; Sagawa, Naoki; Takada, Chie; Momose, Takumaro; Takasaki, Koji
no journal, ,
Cantarel, V.; Yamagishi, Isao
no journal, ,